(a) Technical Field
The present invention relates to, in a lithium secondary battery, a battery cell structure, which has electrochemical stability between an electrode and an electrolyte, and improves ion conductivity while applying a solid electrolyte.
(b) Background Art
Generally, Lithium Ion Batteries have been applied to portable information technology (IT) electrical devices and small electronic devices due to their high energy density per unit weight and their easiness of design. And recently, the batteries have been developed in larger sizes and applied as a power source for electric cars and a power source for storage of electric power according to development of alternative energy sources.
Among the lithium ion batteries, the lithium secondary battery is composed of the cathode and the anode, an electrolyte and a separator, and when discharging, oxidation occurs by deintercalation of lithium ions in the anode and reduction occurs by intercalation of the lithium ions in the cathode. Further, when charging, oxidation occurs by deintercalation of the lithium ions in the cathode and reduction occurs by intercalation of the lithium ions in the anode. Furthermore, the electrolyte does not show conductivity to electrons but only shows ionic conductivity, and is configured to transfer the lithium ions between the cathode and the anode.
In the lithium secondary battery, the lithium ion intercalated into the electrode becomes a medium storing electrical energy in the electrode by forming charge neutralization with electrons coming into the electrode. Accordingly, the amount of the ion intercalated into the electrode to form the charge neutralization controls the amount of the electrical energy, that can be stored in the battery. Basic performances of the lithium secondary battery such as operating voltage and energy density are determined by the materials making the cathode and the anode, but to obtain increased battery performances, the electrolyte intercalated between the anode and the cathode should have increased ionic conductivity, electrochemical stability, thermal stability and the like. In consideration of the reduction with the anode and the oxidation with the cathode, the electrolyte should be electrochemically stable in the corresponding electric potential range.
In the past, lithium salts and organic solvents were mainly used as components of the electrolyte, but when using the said liquid electrolytes, the risk of battery explosion under high temperature and high voltage circumstances increased. Accordingly, a solution applying a solid electrolyte instead of the conventional liquid electrolyte has been developed, but when applying the solid electrolyte, the battery was electrochemically instable and the electrical conductivity of the lithium ion decreased.
The description provided above as a related art of the present invention is just for helping understanding the background of the present invention and should not be construed as being included in the related art known by those skilled in the art.